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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let arr=[1,3,5,8,11,23]
        let index=2
        let arr1=arr.splice(0,index).concat(arr.splice(index-1,arr.length))
        console.log(arr1)
        // let arr1=arr.find((item,key)=>{
        //     return key!=3
        // })
        // console.log(arr1)
        
var s = new Set(arr);
s.delete(index);

    </script>
</body>
</html>